Complex transition metal phosphonates

ABSTRACT

The complex transition metal phosphonates include one or more of compounds with the chemical formula: (1) AxMy(R(PO3)2)z; (2) AxMy(RPO3)z; (3) AxMy(R(PO3)2; nHO; (4) AxMy(RPO3); nH2O; and (5) AxMy(R(PO3)2)z(X)t, where A is an alkali metal or an alkaline earth metal, M is a divalent or trivalent transition metal, R is an organic group, and X is OH, F or CI. For example, A is Li, Na, K, Cs, Rb, Mg, Ca and/or combinations thereof. M is Ni, Co, Mn, Fe, Cr, V, Ti, Cu and/or combinations thereof. R is a C1-C5 alkyl group; e.g., CH2, C2H4, or C3H6, The complex transition metal phosphonates can be used as cathode or anode materials for rechargeable batteries.

TECHNICAL FIELD

The present invention relates to phosphonates, and particularly tophosphonates as electroactive materials for rechargeable batteries.

BACKGROUND ART

The use of rechargeable batteries has increased substantially in recentyears as global demand for technological products such as laptopcomputers, cellular phones, and other consumer electronic products hasrapidly increased. One popular type of rechargeable battery is thelithium ion battery. Compared to other types of rechargeable batteries,lithium to ion batteries provide high energy densities, lose a minimalamount of charge when not in use, and do not exhibit memory effects. Dueto these beneficial properties, lithium ion batteries have foundwidespread use in various electronic fields such as cell phones andlaptop computers. The high energy density characteristics of thesebatteries mean that they can also be used in aerospace, military andvehicle applications.

A lithium ion rechargeable battery cell typically comprises an anode, acathode and an electrolyte. Traditional lithium ion rechargeablebatteries have employed liquid electrolytes, such as a lithium-saltelectrolyte (e.g., LiPF₆, LiBF₄, or LiClO₄) mixed with an organicsolvent (e.g., alkyl carbonate). As the battery is discharged to produceelectrons, the electrolyte provides a medium for ion flow between theelectrodes, and the electrons flow between the electrodes through anexternal circuit. However, the existing rechargeable batteries (e.g.,lithium ion batteries) are incapable of operating safely over a widerange of temperatures of interest. The energy density of existingrechargeable batteries is also inadequate for many applications. Themobility and diffusion of the electrolyte within the electrode is alsonot efficient. Thus, complex transition metal phosphonates solving theaforementioned problems are desired.

DISCLOSURE OF INVENTION

The complex transition metal phosphonates include one or more ofcompounds with the chemical formula: (1) A_(x)M_(y)(R(PO₃)₂)_(z); (2)A_(x)M_(y)(RPO₃)_(z); (3) A_(x)M_(y)(R(PO₃)₂)_(z).nH₂O; (4)A_(x)M_(y)(RPO₃)_(z).nH₂O; and (5) A_(x)M_(y)(R(PO₃)₂)_(z)(X)_(t), whereA is an alkali metal or an alkaline earth metal, M is a divalent ortrivalent transition metal, R is an organic group, and X is OH, F or Cl.For example, A is Li, Na, K, Cs, Rb, Mg, Ca and/or combinations thereof.M is Ni, Co, Mn, Fe, Cr, V, Ti, Cu and/or combinations thereof. R is aC₁-C₅ alkyl group; e.g., CH₂, C₂H₄, or C₃H₆. The complex transitionmetal phosphonates can be used as cathode or anode materials forrechargeable batteries.

These and other features of the present invention will become readilyapparent upon further review of the following specification anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the charge/discharge curves ofNa₂Co(O₃P—CH₂—PO₃), recorded at room temperature, at the rate of 20mA/g.

FIG. 2 is a graph showing a cyclic Voltammogram curve (CV) ofNa₂Fe(O₃P—CH₂—PO₃) recorded at room temperature between 1.5-5 V vs.Na⁺/Na, with a scanning rate of 0.2 mVs⁻¹.

Similar reference characters denote corresponding features consistentlythroughout the attached drawings.

BEST MODES FOR CARRYING OUT THE INVENTION

The complex transition metal phosphonates include one or more ofcompounds with the chemical formula: (1) A_(x)M_(y)(R(PO₃)₂)_(z); (2)A_(x)M_(y)(RPO₃)_(z); (3) A_(x)M_(y)(R(PO₃)₂)_(z).nH₂O; (4)A_(x)M_(y)(RPO₃)_(z).nH₂O; and (5) A_(x)M_(y)(R(PO₃)₂)_(z)(X)_(t), whereA is an alkali metal or an alkaline earth metal, M is a divalent ortrivalent transition metal, R is an organic group, and X is OH, F or Cl.For example, A is Li, Na, K, Cs, Rb, Mg, Ca and/or combinations thereof.M is Ni, Co, Mn, Fe, Cr, V, Ti, Cu and/or combinations thereof. R is aC₁-C₅ alkyl group, e.g., CH₂, C₂H₄, or C₃H₆. X is OH, F, or Cl.

The complex transition metal phosphonates can be used as electroactivematerials for rechargeable batteries, e.g., Na-ion, K-ion, Li-ion andMg-ion batteries. In particular, the complex transition metalphosphonates can be used as anode and/or cathode materials forrechargeable batteries. The complex transition metal phosphonates can beused as insertion materials that enable the mobility and diffusion ofLi, Na; K, Cs, Rb, Mg and Ca ions. The complex transition metalphosphonates can have a crystalline structure or amorphous state. Thecrystalline structure can depend upon the A:M ratio. The A:M ratio canbe from about 0.5 to about 3. For example, the crystalline structure ofthe phosphonates can be tuned depending upon the ratio A/M (from 0.5 to3) wherein the degree of condensation of the [MO_(n)] coordinationpolyhedra is let to vary from isolated [MO_(n)] groups to corner or edgesharing groups.

In some cases, the complex transition metal phosphonates can bedissolved in carbonate, ether or water for use as soluble activematerials for flow battery applications. The complex transition metalphosphonates can be made by ionothermal methods and/or solvothermalmethods using alkyl-phosphonate, as is known in the art. Ionothermalmethods are described, for example, in Recham, N. et al., “A 3.6 Vlithium-based fluorosulphate insertion positive electrode forlithium-ion batteries,” Nature Mater. 9: 68-74 (2010) (preparation ofinorganic materials). Solvothermal methods are described, for example,in Journal of Power Sources, Volume 210: 47-53 (2012) (preparation ofLiFePO₄ cathode materials).

In the ionothermal method, the complex transition metal phosphonates areprepared using an ionic liquid. Ionic liquids include room-temperaturemolten salts with negligible vapor pressure, exhibiting properties ofnon-flammability, high thermal stability and wide liquid range that canallow the use of high temperature preparation. For example, transitionmetal acetate, sodium acetate and alkyl phosphates are dissolved in theionic liquid, such as ethyl methyl imidazolium compound, and heated at120° C. for 12 hours. Then, the ionic liquid solvent is removed byvacuum evaporation method and the resultant mixture is heated on theoven at a temperature of 250° C. for 8 hours. In the solvothermalmethod, the same precursors (transition metal acetate, sodium acetateand alkyl phosphate) are mixed in a stainless steel autoclave usingethylene glycol as a solvent. The mixture is heated under pressure at160° C. for about 6 hours. The autoclave allows the reaction to beconducted without the evaporation of the solvent. The mixture isrecovered and heated in the oven at a temperature of 250° C. for 8hours. The following examples will further illustrate the synthesisprocess for the complex transition metal phosphonates.

Example 1

The disodium iron methylene bisphosphonate Na₂Fe(O₃P—CH₂—PO₃) wasobtained by solvothermal method from a mixture of methylenebisphosphonicacid, FeSO₄.7H₂O, NaOH, and ethylene glycol. A certain amount ofFeSO₄.7H₂O and methylenediphosphonic acid with a mole ratio of 1/1 weredissolved in 20 ml ethylene glycol (EG) solution, and the pH wasadjusted to 10 by adding amounts of NaOH (1M). The mixture was keptstirring for additional half hour at 50° C. After that, the mixtureproducts were transferred inside a 40 ml stainless steel autoclave andheated at 200° C. for 4 days. The final products were washed three timeswith distilled water and dried at 50° C. in a vacuum oven overnight.

Example 2

The disodium cobalt methylene bisphosphonate Na₂Co(O₃P—CH₂—PO₃) wasobtained by solvothermal method from a mixture of methylenediphosphonicacid, CoSO₄.6H₂O, NaOH, ethylene glycol and water. A certain amount ofCoSO₄.6H₂O and methylenediphosphonic acid with a mole ratio of 1/1 weredissolved in 20 ml ethylene glycol (EG/H₂O) solution, and the pH wasadjusted to 10 with NaOH. The mixture was kept stirring for additionalhalf hour at 50° C. After that, the mixture products were transferredinside a 40 ml stainless steel autoclave and heated at 200° C. for 3days. The final products were washed three times with distilled waterand dried at 50° C. in a vacuum oven overnight.

Example 3

The sample of Example 2 was tested as cathode material for sodiumbatteries. The working electrodes composite was prepared by mechanicalmixing of 60 wt. % active material with 30 wt. % Super P carbon and 10wt. % polyvinylidene fluoride as polymer binder. The electrode wasprepared by casting the slurry onto aluminum foil with a doctor bladeand drying in a vacuum oven at 110° C. overnight. The CR2032 coin-typecells were assembled with pure sodium foil as the counter electrode, andglass fiber as the separator in an argon-filled glove box. Theelectrolyte was 0.2 mol/L NaPF₆ dissolved in a 1:1 mixture of ethylenecarbonate (EC) and propylene carbonate (PC). Electrochemical experimentswere carried out with a multichannel potentiostat galvanostat. FIG. 1shows the galvanostic curve with a reversible electrochemical activityat 4.2V.

Example 4

The sample of Example 1 was tested as cathode material for sodiumbatteries. The working electrodes composite was prepared by mechanicalmixing of 60 wt. % active material with 30 wt. % Super P carbon and 10wt. % polyvinylidene fluoride as polymer binder. The electrode wasprepared by casting the slurry onto aluminum foil with a doctor bladeand drying in a vacuum oven at 110° C. overnight. The CR2032 coin-typecells were assembled with pure sodium foil as the counter electrode, andglass fiber as the separator in an argon-filled glove box. Theelectrolyte was 0.2 mol/L NaPF6 dissolved in a 1:1 mixture of ethylenecarbonate (EC) and propylene carbonate (PC). Electrochemical experimentswere carried out with a multichannel potentiostat galvanostat, FIG. 2shows the cyclic voltammetry curves having an oxidation peak at 3.2V anda reduction peak at 2.5V.

It should be understood that a rechargeable battery having an electrodemade from the present complex transition metal phosphonate may take theform of a lithium-ion battery, a lithium air battery, a lithium sulphurbattery, a lithium battery, a sodium-ion battery, a sodium battery, amagnesium-ion battery, a magnesium battery, a potassium-ion battery, apotassium battery, a flow battery or the like.

It is to be understood that the present invention is not limited to theembodiments described above, but encompasses any and all embodimentswithin the scope of the following claims.

We claim:
 1. A complex transition metal phosphonate having a formulaselected from the group consisting of A_(x)M_(y)(R(PO₃)₂)_(z),A_(x)M_(y)(RPO₃)_(z), A_(x)M_(y)(R(PO₃)₂)_(z).nH₂O,A_(x)M_(y)(RPO₃)_(z).nH₂O and A_(x)M_(y)(R(PO₃)₂)_(z)(X)_(t), where A isan alkali metal or an alkaline earth metal; M is a divalent or trivalenttransition metal; R is an organic group; X is OH, F, or Cl; and n is thenumber of water molecules in hydrated phosphonates.
 2. The complextransition metal phosphonates of claim 1, wherein A is selected from thegroup consisting of of Li, Na; K, Cs, Rb, Mg and Ca.
 3. The complextransition metal phosphonates of claim 1, wherein M is selected from thegroup consisting of Ni, Co, Mn, Fe, Cr, V, Ti, and Cu.
 4. The complextransition metal phosphonates of claim 1, wherein R is a C₁-C₅ alkylgroup.
 5. An electrode for a rechargeable battery, comprising anelectrode made from a complex transition metal phosphonate according toclaim
 1. 6. The electrode for a rechargeable battery according to claim5, wherein the electrode comprises a cathode.
 7. The electrode for arechargeable battery according to claim 5, wherein the electrodecomprises an anode.
 8. A rechargeable battery having an electrode madefrom a complex transition metal phosphonate according to claim 1, thebattery being selected from the group consisting of a lithium-ionbattery, a lithium air battery, a lithium sulphur battery, and a lithiumbattery.
 9. A rechargeable battery having an electrode made from acomplex transition metal phosphonate according to claim 1, the batterybeing selected from the group consisting of a sodium-ion battery and asodium battery.
 10. A rechargeable battery having an electrode made froma complex transition metal phosphonate according to claim 1, the batterybeing selected from the group consisting of a magnesium-ion battery anda magnesium battery.
 11. A rechargeable battery having an electrode madefrom a complex transition metal phosphonate according to claim 1, thebattery being selected from the group consisting of a potassium-ionbattery and a potassium battery.
 12. A rechargeable battery having anelectrode made from a complex transition metal phosphonate according toclaim 1, the battery being a flow battery.
 13. The complex transitionmetal phosphonates of claim 1, wherein the complex transition metalphosphonate is soluble in a solvent selected from the group consistingof carbonate solvents, ether solvents, water, and combinations thereof.14. A complex transition metal methylene bisphosphonate having a formulaselected from the group consisting of A_(x)M_(y)(R(PO₃)₂)_(z),A_(x)M_(y)(RPO₃)_(z), A_(x)M_(y)(R(PO₃)₂)_(z).nH₂O,A_(x)M_(y)(RPO₃)_(z).nH₂O and A_(x)M_(y)(R(PO₃)₂)_(z)(X)_(t), where A isan alkali metal or an alkaline earth metal; M is a divalent or trivalenttransition metal; R is an organic group; X is OH, F, or Cl; and n is thenumber of water molecules in hydrated phosphonates.
 15. The complextransition metal methylene bisphosphonate of claim 14, wherein theformula comprises Li₂Fe(CH₂(PO₃)₂)₁.
 16. The complex transition metalmethylene bisphosphonate of claim 14, wherein the formula comprisesNa₂Fe(CH₂(PO₃)₂)₁.
 17. The complex transition metal methylenebisphosphonate of claim 14, wherein the formula comprisesNa₂Co(CH₂(PO₃)₂)₁.